We will build a portable instrument for quick, easy, and non-invasive, assessment of dietary zinc deficiency. Our proposed diagnostic measurements can be done in just 2-3 minutes per subject, with spectroscopic readings taken off one of the subject's FIGURE 1. fingernails. Our product will use a low-energy, nanosecond, laser pulse to interrogate the fingernail surface by creating a spark (plasma) and will quantify the light emissions (spectral lines) from that brief fingernail plasma. (We principal investigators have done this on our own fingernails many times. The minuscule laser pop can be felt, but does not hurt and leaves no mark.) We show below that we can detect and quantitate zinc (and other elements) in the nail plasma for an accurate, ratiometric measurement solution. A typical fingernail represents 3-to-4 month's growth, and by systematically moving the point of plasma creation along the nail from proximal to distal, we can survey ~ 3-4 months of the subject's recent zinc nutritive history. (Measurement of other nutrients and toxins such as Fe, Cu, Pb or Hg can be added in future products in our line. This analytical method we are using is called Laser-Induced Breakdown Spectroscopy (LIBS), and it is a new variant of what we used to call atomic emission spectroscopy. Modern solid-state lasers, CCDs, photodiodes, and ICs have allowed the entire instrument to be shrunk to the size and form-factor shown for the Kigre LIBS product in Figure1. (NOTE: We added to the LIBS instrument picture a second picture of a typical pulse oximeter to show how our optical fibers would be directed to the fingernail.) Complete, portable LIBS instruments are commercially available (e.g., Fig 1) for ~ $20-$30K, and they can be run for hours on 1A-12V battery weighing ~10 pounds. Thus, the instruments we develop can certainly be field-portable and easily used in schools, clinics, exam rooms, nursing homes, or mobile health-Fair units. The Significance of our invention is that it will facilitate detection and informed-remediation of dietary zinc deficiecy. Such deficiency affects about 1/3 of the world's population and is especially devastating to young children. As things stand now, in 2012, the only way to diagnose zinc deficiency is to draw 3-5 mL of venous blood, centrifuge it in a suitable collection tube, then send the sample to an ICPMS or AAS laboratory for instrumental analysis requiring complex and expensive procedures. This means that even US citizens at risk are generally not tested for zinc deficiency. Zinc deficiency is widespread among American children, especially the poor and minorities, where deficiency rates can reach 30% among inner city African American and rural Hispanic youth. The stunting of physical and cognitive development of the young from zinc deficiency is wide-spread, and tragic. The other US population at risk is the elderly, among whom various poor food choices and behaviors lead as many as half of those admitted to hospital to be clinically zinc deficient. Such deficiency weakens the immune defenses of patients and exacerbates numerous ailments. The innovation we bring is to adapt a novel and essentially untried solution to a long-standing clinical problem. We will be inventing all of the mechanical, electrical, and bio-analytical systems, and algorithms that will allow LIBS to be used in the field by health care workers. There are two main problems that we must solve. First, the raw intensity of the zinc atomic emissions must be combined with emission intensities from other fingernail elements in order to generate an accurate, ratiometric measurement of fingernail zinc. For this, we will do LIBS determinations on nail clippings, then measure the zinc in the same clippings by our reference method, which is stable-isotope-dilution ICP mass spectrometry. We will iteratively adjust and modify our LIBS procedures until we can duplicate the stable-isotope dilution values. The second problem to solve will be the elucidation of the relationship between a subject's fingernail zinc and his or her zinc nutritional status. For that, e will compare LIBS measurements from fingernails with the blood-based gold standard measurements of zinc nutritional status, using subjects from both a cross-sectional and a longitudinal zinc-deficiency study.